The invention relates to a method for selectively coating glass tubes with a metallic mirror surface.
Metal-coating methods for producing flat mirrors, curved mirrors, paraboloid grooved mirrors, thermos flasks, Christmas tree balls, etc. are generally known. The metal-coating layer is applied there with the reaction solutions by spraying or swivelling the body to be metal-coated. The entire surface area of the respective object is coated.
Depending on the object the requirements may differ, In the case of polished plate glass the structure is important in the sequence of glass, mirror, copper, and lacquer. In the case of thermos flasks the optical aspect is entirely irrelevant.
Special requirements are placed on glass tubes which are metal-coated and are used as vacuum tube collectors. The relevant aspect is to provide the interior surface of the respective glass tube with a reflective layer, namely one half of the interior surface, which occurs in such a way that the reflective surface has the shape of a cylindrical shell. Such cylindrical shell extends over the entire length of the glass tube or a relevant part thereof.
A known method consists of introducing a mirror in the shape of a cylindrical shell into the respective glass tube. This mirror consists of aluminum sheet, for example.
The disadvantages of such a solution are evident. The introduction of the aluminum sheet is a complex process. The workmanship of the completed, inwardly reflective glass tube is unsatisfactory.